Substituted groups-directed assembly of Cd(ii) coordination polymers based on 5-R-1,3-benzenedicarboxylate and 4,4'-bis(1-imidazolyl)bibenzene: syntheses, structures and photoluminescent properties

Abstract

Hydrothermal reactions of CdCl₂·2.5H₂O with 4,4'-bis(1-imidazolyl)bibenzene (bimb) and 1,3-benzenedicarboxylate (1,3-H₂BDC), 5-methyl-1,3-benzenedicarboxylate (5-Me-1,3-H₂BDC), 5-amino-1,3-benzenedicarboxylate (5-NH₂-1,3-H₂BDC), 5-hydroxy-1,3-benzenedicarboxylate (5-HO-1,3-H₂BDC), 5-nitro-1,3-benzenedicarboxylate (5-NO₂-H₂1,3-BDC), or 5-sulfo-1,3-benzenedicarboxylate (5-HSO₃-1,3-H₂BDC) resulted in the formation of six Cd(II) coordination polymers, [Cd(5-R-1,3-BDC)(bimb)]_n (R = H (1), R = Me (2), R = NH₂ (3), R = OH (4)), {[Cd₂(H₂O)(5-NO₂-1,3-BDC)₂(bimb)]·2H₂O}_n (5) and [Cd(5-SO₃-1,3-HBDC)(bimb)]_n (6). Compounds 1–6 were characterized by elemental analysis, IR, powder X-ray diffraction and single-crystal X-ray diffraction. 1–4 exhibit similar 3D frameworks in which 2D [Cd₄(5-R-1,3-BDC)₄]_n (R = H, Me, NH₂ and OH) layers are interlinked by bimb ligands. 5 has a two-fold interpenetrating 3D framework in which 1D [Cd₂(5-NO₂-1,3-BDC)₂]_n chains are interconnected by bimb ligands. 6 shows a 3D (3,5)-connected framework in which 2D [Cd₂(5-SO₃-1,3-HBDC)₂]_n networks are bridged by bimb ligands. The Schläfli symbols for these six 3D nets are (4·6²)(4·6⁶·8³) (1–4), (4²·6)(4²·6·10²·12) (5) and (4·6·8)(4·6⁵·8³·10) (6). The solid state photoluminescent properties of 1–6 were also investigated.